Analysis of the Damage of Uncoated Polymeric Surfaces During Scratching

Attempts have been made to correlate the scratch behaviour and basic material properties of polymers and a correlation has been established between the scratch damage and friction coefficient. However, no clear relationship has yet been established between the bulk response and scratch damage. The scratch behaviour of three solid polymers (PMMA, PC and CR39) was investigated to determine how the behaviour of the bulk material affects the scratch resistance. The bulk damage responses of these materials are well known: crazing, shearing and cracking, respectively. The surfaces were scratched under progressive scratch loading and an imaging system was used to record real time photographs of the in-situ contact area and scratch damage. PMMA exhibited crazing under the apex of the scratching tip while the shearing of PC started under the front part of the contact area and cracking appeared in CR39 at the rear edge of the contact. Numerical simulations confirmed these damage mechanisms.